Objective: The spikes of Schizonepeta tenuifolia from different habits were predicted by UV-Vis spectrum. Method: The dimensions of spectrum data obtained from ten habits were reduced by principal component analysis, and the first six new variables with 99.82% of cumulative reliability were put into the backpropagation neural network for model building. Result: The recognition rate of backpropagation neural network coupled with principal component analysis (PCA-BPNN) was 100%, and its mean square error was 0.001 0. Conclusion: PCA-BPNN can be used for the classifying of spikes of S. tenuifolia from different producing area, and this method is simple and fast.

Objective: To study the plasma protein binding rate of schizonepetin in rats. Methods: Equilibrium dialysis was used to determine the in vitro binding rate of schizonepetin to rat plasma. A HPLC method for the determination of schizonepetin was established and then the plasma protein binding rate in rats was calculated. Results: Schizonepetin and internal standard were separated completely with no interference from other ingredients. The calibration curve of schizonepetin was in good linearity over the range of 0.05~50.3 μg·mL -1. The intra-day and inter-day precision and recovery of schizonepetin met the requirements of methodology. The plasma protein binding rate of schizonepetin at low, middle and high concentrations (0.08, 0.63, 6.30 μg·mL -1) were (62.23±1.25)%, (62.71±0.04)% and (63.99±0.79)%, respectively. Conclusion: The method is simple, rapid, accurate, and sensitive, and it can meet the requirement for analysis method of biological samples. Schizonepetin has medium plasma protein binding rate in rats, with no significant relation to drug concentrations in dialyzate.

Objective: To study the gastrointestinal absorption kinetics of schizonepetin in rats. Methods: The drug concentration by in situ perfusion in rats was determined by HPLC and the volume of perfusion fluid was adjusted by Phenol red labeling. Results: The hourly absorption percentages of three different drug concentrations (1.84, 3.68, and 7.36 μg/mL) in stomachs were (19.47 ± 0.69) %, (21.66 ± 1.92) %, and (26.51 ± 1.25) %, respectively. The absorption rate constants (Ka) of three different concentrations in intestine were (0.203 ± 0.007), (0.159 ± 0.011), and (0.134 ± 0.012) h-1, respectively, which had significant differences among them (P<0.05). Conclusion: Schizonepetin might be absorbed in stomachs via passive transport mechanism and in intestine via active transport mechanism.